Within semiconductor integrated circuits (ICs), fuses can be used to program and permanently store information. Additionally, fuses can be used to form or break electrical connections within ICs. A fuse comprises a fuse link electrically coupling two separate electrical nodes, e.g., an anode and a cathode. Upon the application of a particular stressor to the fuse, the fuse link can be “broken.” The break in the fuse link creates an increase in a resistance of a conductive path, possibly an open circuit, between the two electrical nodes. Thus, the fuse has two different programmable states. A first programmable state exists when the fuse has a low resistance in a conductive path through the fuse prior to breaking the fuse link. A second programmable state exists when the fuse has a high resistance in the conductive path through the fuse subsequent to breaking the fuse link.
One type of programmable fuse used within ICs is a laser fuse. The laser fuse is programmed by exposing the material of the fuse link to sufficient laser energy to vaporize the material. However, the level of laser energy necessary to break the fuse link is often capable of damaging devices neighboring the laser fuse being programmed. The need to expose laser fuses to laser energy also prevents laser fuses from being programmed subsequent to IC packaging.
Another type of fuse is the electrically programmable fuse, which is often referred to as an e-fuse. To program the e-fuse, a voltage potential is applied across the conductive fuse link, typically formed of a silicided polysilicon layer, via the cathode and the anode. The applied voltage potential is of sufficient magnitude, and constant polarity, to initiate electromigration and dopant depletion in the silicided polysilicon layer forming the fuse link.
Electromigration refers to a transportation of material by the gradual movement of ions in a conductor due to a momentum transfer between conducting electrons and diffusing metal atoms. Current traveling through the e-fuse generates electromigration effects that migrate silicide material away from one or more portions of the cathode, the anode, or the fuse link regions. The migration results in a higher resistance in the conductive path through the e-fuse. Typically, a large current density is required to flow through the fuse link to induce electromigration within the e-fuse.